The chemical bonds that hold molecules together are composed of electrons, and in order to study these microscopic systems, electronic structure calculations are often employed. This thesis describes the results from several studies that use computational techniques to investigate a variety of bonding interactions. The systems presented range from small water clusters to large DNA quadruplexes. High-level computational techniques, such as ab initio and density functional theory methods, were applied as well as the quantum theory of atoms in molecules (AIM). AIM uses the gradient to analyze the electron density, partitioning the molecule into atomic fragments. Once the system is partitioned, individual atomic contributions to molecular properties can be determined. Furthermore, bonding interactions can be identified by the presence of a specific type of critical point within the topology. These two facets of AIM are exploited throughout this thesis. The first project presented is a theoretical investigation of the exact electronic structure of hydrated electrons. Whether the excess electron resides within a central cavity or is smeared out over the surface of the cluster remains a contentious issue. In an attempt to investigate this dilemma from a novel viewpoint, AIM was used to analyze the electron density of small anionic water clusters up to ten water molecules. The results suggest that the preferred site of binding is dictated by the relative orientation of the non-hydrogen-bonded hydrogen atoms. At the other end of the spectrum, the largest systems investigated were several guanine quadruplexes that can form in telomeric regions of DNA. In light of the attention these structures have received as potential therapeutic agents, a clear understanding of their formation is mandatory. The study presented here is a detailed investigation of the electronic energy changes associated with the folding of the quadruplex from the single-stranded telomere. After devising a novel method to display the atomic energy data, several interesting trends in the energy changes were identified. Ultimately, the data presented could help to guide future drug development endeavours, highlighting one of the many practical applications of computational methods.

No description available.

Conventional primary Li/CFx batteries employ graphite and polyvinylidene fluoride additives in the cathodes. These additives usher in some un-desired side-effects, such as lower battery capacities (mAh/g) and smaller current densities (mA/g). An innovative pretreatment was developed in this research in which CFx was subject to a “solvated electron” reduction to obtain a thin layer graphitic carbon coating on the CFx particle surfaces. Resistivity tests revealed that these partially reduced CFx particles have a higher conductivity at comparable graphitic carbon contents. Electrochemical discharge reactions demonstrated that batteries made from the reduced CFx were superior to the conventional batteries with higher current densities and higher capacities achieved. Impedance spectroscopy (EIS) studies found out that the reduced CFx particles have smaller cell reaction resistances, smaller double layer/intercalation capacitances and smaller mass transport resistances. It appears that use of reduced CFx has the potential to replace the conventional CFx plus additives as a cathode material in Li/CFx batteries.

The unique compressive, optical, and biocompatible properties of silicone hydrogels allow them to be used in a wide variety of applications in the biomedical field. However, the relatively weak mechanical behavior, as well as the highly deformable nature of these elastomeric materials, presents a myriad of challenges when attempting to understand their constitutive and fracture properties in order to improve hydrogel manufacturing and performance in applications. In this thesis, a series of experimental techniques were developed or adapted from common engineering approaches in order to investigate the effects of rate and temperature on the viscoelastic constitutive and fracture behavior of two solvated semi-interpenetrating polymer network silicone hydrogel systems. Viscoelastic characterization of these material systems was performed by implementing a series of uniaxial tension and dynamic mechanical analysis shear tests in order to generate relevant master curves and corresponding thermal shift factors of such properties as shear relaxation modulus, dynamic moduli, and the loss factor. Concurrently, the cohesive fracture properties were studied by utilizing a "semi-infinite" strip geometry under constrained tension in which thin pre-cracked sheets of these cured hydrogels were exposed to several different loading conditions. Fracture tests were performed over a relevant range of temperatures and crosshead rates to determine and generate a master curve of the subcritical strain energy release rate. Experimental methods utilizing high-speed camera images and digital image correlation to monitor viscoelastic strain recovery in the wake of a propagating crack were explored. The results from this thesis may prove useful in an investigation of the interfacial fracture of these hydrogel systems on several different polymer substrates associated with an industrial manufacturing problem. / Master of Science

Parmi tous les nanomatériaux carbonés, les nanodiamants de détonation (NDs) possèdent des propriétés physico-chimiques exceptionnelles faisant d’eux un matériau idéal pour les applications en biologie. Aujourd’hui, la production industrielle permet de synthétiser des NDs ayant une taille de 5 nm comportant un cœur diamant et une enveloppe de surface possédant différentes terminaisons. La chimie de surface des NDs peut être modifiée par recuit ou par plasma donnant des NDs négativement ou positivement chargés en suspension dans l’eau. Notre équipe a récemment démontré des propriétés radiosensibilisantes des NDs hydrogénés par plasma (H-NDs) sur des lignées cellulaires cancéreuses radiorésistantes. Ces résultats prouvent leur aptitude thérapeutique comme agents radiosensibilisants. Cependant, les mécanismes impliqués dans cet effet ne sont pas bien compris. L’objectif principal de ce travail de thèse est d’étudier le comportement des NDs en suspension dans l’eau sous irradiation (rayons X et gamma) et de mesurer la production d’espèces réactives de l’oxygène (ROS) en particulier les radicaux hydroxyles HO. Des expériences complémentaires ont permis de détecter la production d’électrons solvatés (eaq). La détection des radicaux HO et des électrons solvatés (eaq) a été réalisée en utilisant une sonde fluorescence, la 7 OH-coumarine, dans des atmosphères différentes (air and N2O/O2). Différentes chimies de surface ont été comparées (oxydée, hydrogénée, graphitisée en surface) préparées à partir de la même source de NDs. En parallèle, les propriétés colloïdales et la stabilité de ces NDs dans l’eau ont été étudiées à court et à long terme en fonction de leur chimie de surface. Une surproduction de radicaux HO a été mesurée pour les H-NDs hydrogénés par les deux méthodes et pour les NDs recuites sous vide à 750°C. De plus, une surproduction d’électrons solvatés a été mise en évidence pour les H-NDs. Ces résultats sont discutés en fonction de la chimie de surface, la stabilité colloïdale et les interactions spécifiques des molécules d’eau avec les NDs. / Among all nanocarbons, detonation nanodiamonds (NDs) possess outstanding chemical and physical properties suitable for bio-applications. Well-controlled mass production provides NDs with a primary size of 5 nm made of a diamond-core and a shell-coating containing various surface terminations. Surface chemistry of NDs can be tuned via thermal or plasma treatments providing either positively or negatively charged NDs in water suspension. Our group recently showed that plasma hydrogenated NDs (H-NDs) behave a radiosensitizing effect on radioresistant cancer cell lines providing potential therapeutic abilities as radiosensitizing agents. Nevertheless, the mechanisms involved behind this effect are not currently well understood. The main goal of this PhD is to study the behaviour of NDs suspended in water under ionizing radiations (X-ray and Gamma) and to investigate the production of reactive oxygen species (ROS), in particular hydroxyl radicals (HO). Additional experiments allow to detect also produced solvated electrons (eaq). The detection of HO radicals and solvated electrons was realized in the presence of a fluorescence probe, the 7 OH-coumarin, under various atmospheres (air and N2O/O2). Starting from the same source of NDs, different surface chemistries were compared (oxidized, hydrogenated and surface graphitized). In parallel, colloidal properties and stability of these modified NDs in water with respect to their surface chemistry were investigated at short and long term. An overproduction of HO was observed for H-NDs for both hydrogenation methods and vacuum annealed NDs at 750°C. In addition, the production of solvated electrons was confirmed for H-NDs. These results were discussed taking into account the surface chemistry, the colloidal stability and specific interactions of water molecules with NDs.

A espectroscopia de ressonância ciclotrônica de íons foi usada para estudar reações de íons alcóxido, hidróxido, fluoreto, íon-radical óxido, acetileto e amideto com formiatos de alquila; o último íon reage também com N,N-dimetilformamida. Em todos os casos ocorre uma reação de descarbonilação, dando origem a um íon solvatado, que as evidências experimentais indicam ser unido por ponte de hidrogênio. Deslocamentos nucleófilos de grupos ligados ao esqueleto formílico podem ocorrer em casos adequados e em casos especiais ocorre ainda a formação de íons formiato. Os íons solvatados formados a partir de íons fluoreto e alcóxido com formiatos de alquila reagem com álcoois, podendo-se desta meneira estabelecer uma ordem de capacidade de solvatação para os álcoois alifáticos simples. A ordem estabelecida foi: CH3OH < C2H5OH < iso-C3H7OH < tert-C4H9OH. Foram determinadas constantes relativas de velocidade para as reações de vários íons negativos com formiatos de alquila, em sistemas onde se forma mais de um produto. Nos casos mais favoráveis (reações de íons fluoreto) foram calculadas constantes de velocidade absolutas para os vários canais de reação. / Ion-cyclotron resonance spectroscopy has been used to study the reactions between alkoxide, hydroxide, fluoride, O-, acetylide and amide ions with alkyl formates; the last ion reacts also with N,N-dimethylformamide. In all systems a decarbonylation occurs, giving rise to a solvated product ion, held by a hydrogen bond, as evidenced experimentally. Nucleophilic displacement of the formyl group substituents may occur in favorable cases and in a few particular systems the formation of formate ion is observed. The solvated ions formed through the reaction of fluoride or alkoxide ions with alkyl formates can react further with alcohols to establish the intrinsic clustering ability of simple aliphatic alcohols. The order of solvating ability is shown to follow the order CH3OH < C2H5OH < iso-C3H7OH < tert-C4H9OH. In systems where parallel reactions occur, relative rate constants were determined; in the most favorable cases (reactions of fluoride ions), absolute rate constants for the various reaction channels were calculated.

A espectroscopia de ressonância ciclotrônica de íons foi usada para estudar reações de íons alcóxido, hidróxido, fluoreto, íon-radical óxido, acetileto e amideto com formiatos de alquila; o último íon reage também com N,N-dimetilformamida. Em todos os casos ocorre uma reação de descarbonilação, dando origem a um íon solvatado, que as evidências experimentais indicam ser unido por ponte de hidrogênio. Deslocamentos nucleófilos de grupos ligados ao esqueleto formílico podem ocorrer em casos adequados e em casos especiais ocorre ainda a formação de íons formiato. Os íons solvatados formados a partir de íons fluoreto e alcóxido com formiatos de alquila reagem com álcoois, podendo-se desta meneira estabelecer uma ordem de capacidade de solvatação para os álcoois alifáticos simples. A ordem estabelecida foi: CH3OH < C2H5OH < iso-C3H7OH < tert-C4H9OH. Foram determinadas constantes relativas de velocidade para as reações de vários íons negativos com formiatos de alquila, em sistemas onde se forma mais de um produto. Nos casos mais favoráveis (reações de íons fluoreto) foram calculadas constantes de velocidade absolutas para os vários canais de reação. / Ion-cyclotron resonance spectroscopy has been used to study the reactions between alkoxide, hydroxide, fluoride, O-, acetylide and amide ions with alkyl formates; the last ion reacts also with N,N-dimethylformamide. In all systems a decarbonylation occurs, giving rise to a solvated product ion, held by a hydrogen bond, as evidenced experimentally. Nucleophilic displacement of the formyl group substituents may occur in favorable cases and in a few particular systems the formation of formate ion is observed. The solvated ions formed through the reaction of fluoride or alkoxide ions with alkyl formates can react further with alcohols to establish the intrinsic clustering ability of simple aliphatic alcohols. The order of solvating ability is shown to follow the order CH3OH < C2H5OH < iso-C3H7OH < tert-C4H9OH. In systems where parallel reactions occur, relative rate constants were determined; in the most favorable cases (reactions of fluoride ions), absolute rate constants for the various reaction channels were calculated.

Nous étudions la dynamique d’anions hydroxyde et fluorure micro-solvatés dans un agrégat d’eau après photo-excitation. Du fait du coût numérique important des calculs ab-initio et de la faible transférabilité des potentiels modèles de la littérature, nous avons développé un nouveau modèle transférable permettant de décrire l’interaction d’un soluté quelconque avec une molécule d’eau. Nous avons également effectué une étude des propriétés statiques de F^-(H2O)n=1−7 et OH−(H2O)n=1−7 qui sert de référence pour la paramétrisation du modèle et fournit une base à l’interprétation des calculs de dynamique. De cette étude, nous avons déduit le nombre de molécules d’eau nécessaires pour stabiliser le premier état excité de F− et OH−. Nous avons aussi déterminé l’impact de la base sur la description des états excités. Enfin, nous avons mis en évidence un motif géométrique favorable à la recombinaison géminée. L’étude de trajectoires sur le premier état singulet excité pour F^-(H2O)3,5 et OH^-(H2O)3,5 montre des différences de comportement entre le fluorure et l’hydroxyde. Pour F^−, l’électron est très diffus et se transfère en une centaine de femtosecondes à l’eau. Dans le cas de OH^−, à cause du dipôle du radical OH qui maintient l’électron, le transfert de charge ne s’effectue que lorsque le radical OH tourne vers l’agrégat d’eau. Cette différence de comportement entre OH^−et F^−offre une piste pour la compréhension du phénomène de recombinaison géminée rapide observé pour OH^−. Nous avons également étudié le spectre d’énergie de détachement vertical de l’électron pour des agrégats d’eau négativement chargés qui constituent l’un des produits finaux de la dynamique des anions photo-excités. Ces résultats ont été discutés et comparés à l’expérience. Nous avons ainsi pu faire correspondre des structures géométriques aux pics des spectres mesurés expérimentalement. Nous discutons aussi du rôle de l’énergie interne des agrégats sur l’allure des spectres via son impact sur l’évaporation de molécules d’eau. / We study the dynamics of micro-solvated hydroxide and fluoride anions in water clusters after photoexcitation. Because ab-initio calculations are numerically expensive and model potentials from literature lack of transferability, we developed a transferable model, which allows us to describe the interaction between any solute and a water molecule. We have studied the statics properties of F^−(H2O)n=1−7 and OH^−(H2O)n=1−7. The results from this study serve as a basis for the parametrization of the model and for the interpretation of dynamics simulation. From this study, we deduced the number of water molecules needed to stabilize an excited state for F^−and OH^−. We investogated the impact of the basis on the description of the excited states At last, we highlight a favorable motif for geminate recombination. Study of trajectories on the first excited singlet states of F^−(H2O)3,5 and OH^−(H2O)3,5 shows differences in the dynamics between OH^−and F^− For F^−, the excess electron is very diffuse and transferred quickly to the water For OH−, because of the OH dipole, the excess electron remains bound to the neutral . OH, until charge transfer takes place when OH rotate to the water cluster. This difference provides a way to understand the fast geminate recombination process observed for OH^−. We also studied vertical detachment spectra of the electron for negatively charged water clusters which are the final products of the anions dynamics on the first excited state. These results are compared to experience from literature. We associate isomers to the experimentally observed peaks. We discuss the effect of internal energy on the shape of the spectra through water molecules evaporation

Le travail présenté dans cette thèse, s’inscrit dans le domaine d'étude de l'interaction des rayonnements ionisants avec les liquides polaires. Bénéficiant de l’accélérateur d'électrons picoseconde ELYSE, les études ont été menées en utilisant les techniques de la radiolyse impulsionnelle associées à la spectrophotométrie d’absorption résolue en temps dans le domaine de la picoseconde. Ce travail est réparti sur deux chapitres distincts. Le premier aborde l’étude la variation temporelle du rendement radiolytique de l’électron solvaté dans l'eau et les alcools simples. Grâce au système de détection original monté sur l’accélérateur ELYSE, composé d’une lampe flash spécialement conçue pour cette détection et d’une streak-camera utilisée pour la première fois en spectroscopie d’absorption, il a été possible d'enregistrer la totalité du déclin du rendement radiolytique de l’électron solvaté d’une façon continue dans un intervalle de temps allant de la dizaine de picoseconde à quelques centaines de nanoseconde. La capture de l’électron solvaté par le méthylviologène, a été mise à profit pour réévaluer le coefficient d’extinction molaire du spectre d'absorption de l’électron solvaté dans l’eau et l’éthanol à partir des points isobestiques qui apparaissent à l'intersection des spectres d'absorption de l’électron solvaté qui disparaît et du méthylviologène qui se forme au cours de la réaction.Le deuxième chapitre est consacré à l’étude des carbonates organiques liquides, tels que le diméthyle carbonate (DMC), le diéthyle carbonate (DEC) et le propylène carbonate (PC). Cette famille de carbonate qui n’a jamais été étudiée auparavant par radiolyse pulsée, entre dans la composition des électrolytes des batteries notamment au lithium. Les études ont été focalisées sur le PC au vu de ces caractéristiques physico-chimiques, notamment sa constante diélectrique très élevée (64) et son très fort moment dipolaire de 4,9 D. Les premiers résultats ont été obtenus d’abord sur des solutions aqueuses contenant du propylène carbonate afin d'observer les réactions de réduction et d'oxydation du PC par les espèces radiolytiques de l'eau (électron solvaté et radicaux OH). Puis après l’identification (spectrale et cinétique) de l’espèce formée par interaction avec le radical OH comme étant le radical PC• résultant de l'abstraction d'un H de la molécule de PC et l’espèce formée par interaction avec l’électron aqueux comme étant l'anion PC-, d’autres mesures ont été effectuées dans le liquide pur ainsi qu’en présence de certains intercepteurs d’électrons (biphényle, anthracène, naphtalène). Elles ont permis d'accéder au rendement radiolytique de PC- ainsi qu'à l'évaluation de son potentiel redox. Les premiers résultats sur le DEC et le DMC sont aussi exposés dans cette partie, portant dans un premier lieu sur le solvant pur et puis en présence de biphényle. / This work is part of the study area of the interaction of radiation with polar liquids. Using the picosecond electron accelerator ELYSE, studies were conducted using the techniques of pulse radiolysis combined with absorption spectrophotometry Time-resolved in the field of a picosecond.This work is divided into two separate chapters. The first study addresses the temporal variation of the radiolytic yield of solvated electron in water and simple alcohols. Due to original detection system mounted on the accelerator ELYSE, composed of a flash lamp specifically designed for the detection and a streak-camera used for the first time in absorption spectroscopy, it was possible to record the time-dependent radiolytic yields of the solvated electron from ten picoseconds to a few hundred nanoseconds. The scavenging of the electron solvated by methyl viologen, was utilized to reevaluate the molar extinction coefficient of the absorption spectrum of solvated electron in water and ethanol from isobestic points which corresponds to the intersection of the absorption spectra of solvated electron which disappears and methyl viologen which is formed during the reaction.The second chapter is devoted to the study of liquid organic carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC) and propylene carbonate (PC). This family of carbonate wich compose the electrolytes lithium batteries, has never been investigated by pulse radiolysis. The studies were focused on the PC in the light of these physicochemical characteristics, including its very high dielectric constant (64) and its strong dipole moment of 4.9 D. The first results were obtained on aqueous solutions containing propylene carbonate to observe the reactions of reduction and oxidation of PC by radiolytic species of water (solvated electron and OH radicals). Then, after the identification (spectral and kinetic) of the species formed by interaction with the OH radical as the PC• radical resulting from the abstraction of a H from the molecule of PC and the species formed by the interaction with electron as the anion aqueous PC-, other measurements were made in the pure liquid and in the presence of some electron interceptors (biphenyl, anthracene, naphthalene). They give access to the radiolytic yield of PC- and the evaluation of its redox potential. The first results of the DEC and the DMC are also outlined in this section, the pure solvent and then in the presence of biphenyl.

No description available.